# In lab you submerge 100 g of 40°C iron nails in 100 g of

Chapter 8, Problem 5P

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QUESTION:

In lab you submerge 100 g of 40°C iron nails in 100 g of 20°C water (the specific heat of iron is 0.12 cal/g°C.) (a) Equate the heat gained by the water to the heat lost by the nails and show that the final temperature of the water becomes 22.1°C. (b) Your lab partner is surprised by the result and says that since the masses of iron and water are equal, the final water temperature should lie closer to 30°C, half-way between. What is your explanation?

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QUESTION:

In lab you submerge 100 g of 40°C iron nails in 100 g of 20°C water (the specific heat of iron is 0.12 cal/g°C.) (a) Equate the heat gained by the water to the heat lost by the nails and show that the final temperature of the water becomes 22.1°C. (b) Your lab partner is surprised by the result and says that since the masses of iron and water are equal, the final water temperature should lie closer to 30°C, half-way between. What is your explanation?

Solution 5P 0 (a) Let the final temperature be x C Specific heat of water is = 1 cal/g C0 Initial temperature of water = 20 C 0 Mass of water = 100 g Therefore, heat gained by water= mass × specific heat × change in temperature 0 0 = 100 g × 1 cal/g C × (x 20) C = 100(x 20) cal …..(1) Mass of the nails = 100 g Specific heat of iron = 0.12 cal/g C0 Initial temperature of the nail